A novel non-equilibrium partitioning model and the designed strong and ductile Al-7.5Mg-0.5Sc-0.3Zr-0.6Si alloy for selective laser melting

Strong and ductile Al alloys and their design strategy have long been desired for selective laser melting. This work reports a non-equilibrium partitioning model and the correspondingly designed Al-7.5Mg-0.5Sc-0.3Zr-0.6Si alloy. By considering the non-equilibrium partitioning under high cooling rates in selective laser melting, this model properly quantifies the influence of Mg and Si on hot cracking of aluminum. The designed Al-7.5Mg-0.5Sc-0.3Zr-0.6Si alloy exhibits no hot cracks and a much-improved strength-ductility synergy (the yield strength being 412 ± 8 MPa, the uniform elongation being 15.6 ± 0.6 %) much more superior than that of previously reported Al-Mg-Sc-Zr, Al-Mn, etc. A tensile cracking model is proposed to explore the origin of improved ductility. The non-equilibrium partitioning model and the novel Al-7.5Mg-0.5Sc-0.3Zr-0.6Si offer a good opportunity for producing highly reliable aluminum parts by selective laser melting.